When ruptures or cracks occur in underground conduits such as sewer lines, telephone conduits and other non-pressurized underground pipes, it is much less costly to repair these conduits in situ than it is to excavate them for repair or replacement. One known method of in situ conduit repair involves introducing an inflatable, resin coated pipe into the conduit and inflating that pipe with hot, flowing air. The inflated pipe bonds to the ruptured host conduit and is allowed to cure. At the same time, the uncured resin permeates the cracks in the host pipe.
The technique described above suffers from several disadvantages. First, the inflated pipe typically extends from manhole to manhole and is applied to undamaged, as well as ruptured sections, of the conduit. As a result, unnecessary time, material and effort are expanded. And because the cost of the repair is dictated by the linear footage which is patched, this type of repair can prove unduly expansive. Currently, at an expense of approximately $100 per linear foot, it may cost $20,000 to $40,000 to repair a damaged pipe, even where only a very small portion of that pipe is ruptured. Additionally, by patching the entire run of pipe between adjacent manholes, the contractor often covers the discharge openings of pipes which empty into the conduit being repaired. These openings must then be recut by a hydrojet cutter, a water cannon or a grinder. As a result, the cost, time and complexity of the conduit repair operation are increased even further. Additionally, the recutting operation can leave rough edges which can cause leaking, obstructions and other problems in the future.